DC Magnetron Sputtering is a thin film deposition technique. For example, sputtering can occur in an environment containing Argon gas (Ar). A negative DC potential is applied to a conductive metal “target.” A plasma discharge is established to ionize the gas thereby creating Ar+ions. The positively charged Ar+ions accelerate towards the negatively charged target and cause ejection of the target atoms through sputtering, which in turn creates a metal film on an opposing placed substrate.
Introduction of reactive gases such as O2 or N2 can cause the film to take on properties of the compounds created by the reaction of these gases with the deposited metal film. Further ionization and acceleration of these reactive gases can enhance the reactivity between the gas and the film in addition to improving the density of the film as well as influence other film properties such as the film stress, hardness, index and absorption.
Conventional deposition systems are complex and suffer from issues including reduced wafer throughput and material contamination issues, which can limit film quality and require extended preventative maintenance cleaning of the deposition equipment. Conventional deposition systems use a batch chamber where sputter source and ion source are placed in close proximity to one another, resulting in cross talk between their respective plasmas, and where oxidation is simultaneous with film deposition.
In reactive sputtering in a batch system, there is always concern about arcing from the insulating layers that build up on the DC sputtered target. Any layers that form on the sputter target or on the anode of the ion source that are non-conductive can act as a capacitor, which when its charge is built up to the break down voltage of the insulating layer, can discharge, forming an arc. The arc can cause the ejection of particles from this layer into the chamber and onto the substrates. Severe arcing may even shut down the power supplies interrupting the process run. This effect is sometime referred to as poisoning of the target with the reactive gas. Total poisoning of the target can shut down the DC process as the target now appears as an open circuit to the DC supply powering the magnetron.
RF sputtering can be used to circumvent this poisoning effect since RF power is unaffected by insulating materials. However, RF sputtering is a much more inefficient process for power delivery to the target versus heat generated at the target. Asymmetric Bipolar Pulsing the target with devices such as a SPARCLE™ or Pinnacle Plus™ and similar such devices have met with some measure of success but particles can still be ejected from the non-eroded racetrack area of the target and there is also slight reduction in deposition rate. There are also various techniques which apply closed loop controls to the reactive gas mass flow controller (MFC) to curtail target poisoning using plasma emission spectroscopy Speedflow™.
U.S. Pat. No. 8,758,580 discloses a deposition system that produces reacted films in separate sputter and ion beam zones. However, an aperture over the magnetron is required to build up a pressure difference between the argon at the magnetron and the much lower O2 pressure from the ion source. The resulting pressure gradient prevents target poisoning, but at the cost of reduction in target utilization. From a cost of ownership issue this can be potentially problematic even for relatively inexpensive aluminum targets. Further, US 20070151842 A1 discloses producing reacted films in separate zones using a sputter and ion beam zones. Differential pumping of the sputter source is used to prevent target poisoning. Additionally, since the sputtering is performed downward on a circular disc, a uniformity aperture must be used between the target and substrate to tune the film uniformity.
Accordingly, there is a need for a deposition system and method that address the shortcomings described above.